1. Field of the Invention
The present invention relates to an improvement in a ROM card unit having a card package accommodating a ROM card on which ROMs whose contents are earsable by ultraviolet radiation are mounted.
2. Description of the Related Art
In general, read-only memories (ROMS) include the following: a mask ROM whose contents are wirtten by the IC manufacturer as previously specified by the user; a fuse ROM which allows data to be freely written by the user, but does not allow the data to be altered; an erasable programmable read-only memory (EPROM) which allows data to be freely written by the user, and allows its contents to be erased by ultraviolet radiation; and electrically erasable programmable read-only memory (EEPROM) which allows data to be freely written by the user, and allows its contents to be erased by an electrical operation. From the view point of reliability and response speed, EPROMs which allow their contents to be erased by ultraviolet radiation are often used. Therefore, in describing the present invention, a ROM card unit which accommodate EPROMs of the ultraviolet-erasable type (hereinafter simply referred to as "ROMs") will be explained. With such a ROM, data is written by electrically exciting flip-flops corresponding to the bits constituting the data (hence, the contents stored). The data written in this way is erased by radiating ultraviolet light onto the flip-flops of the ROM for a certain period of time, whereby the irradiated flip-flops are, through the supply of energy, brought to their initial state. In order to prevent unwanted natural erasure of written data, a mask seal for preventing transmission of ultraviolet light is adhered to a ROM over an ultraviolet radiation window of the ROM.
FIGS. 6 and 7 show, in front and side views, a conventional ROM card unit. FIG. 8 is a front view of the ROM card of the ROM card unit, and FIG. 9 is an exploded perspective view of the ROM card unit. As shown in these figures, the conventional ROM card unit includes a ROM card board 1, ROMs 2 mounted on the ROM card board 1, ROM mask seals 3 for preventing unwanted erasure of the contents of the ROMs 2, and a connector 4 electrically connected with a pattern (not shown) formed on the ROM card substrate 1. The above-described members 1 to 4 constitute a ROM card. The conventional ROM card unit also includes a card package comprising a card package body 5 for accommodating the ROM card, and a card package cover 6 which is attached to the card package body 5.
With this conventional structure, data stored in ROMs of the ROM card is rewritten by the following process.
When the data stored in the ROMs 2 is to be rewritten, screws 7 joining the card package body 5 and the card package cover 6 together are removed, and the ROM card board 1, with the ROMS, is taken out from the inside of the card package body 5. All the ROM mask seals 3, adhered to the ROMs 2 over ultraviolt radiation windows 2a thereof, are removed to effect the erasure of the contents of the ROMs 2 by ultraviolet radiation. Thereafter, the whole card is subjected to the operation of writing new data into the ROMs 2.
With the above-described construction of the conventional ROM card unit, when, for instance, the data in the ROMs 2 is to be rewritten, it is necessary to remove the card package cover 6, to take out the ROM card board 1, with various members thereon, and to remove the ROM mask seals 3. In addition, there is a risk that the adhesion of the ROM mask seals 3 may deteriorate, thereby making the seals 3 unable to be repeatedly applied.